Wang was taught the rules of chess when he was six years old. He had attended a local youth center with the hopes of being taught Xiangqi (Chinese Chess), however the trainer did not appear. He was introduced to chess that day instead, and almost by accident, his career was launched. Around one year later, Wang played in his first local junior tournament.[3]

In 1999, Wang came third in the Under-10 division of the World Youth Chess Championships in Oropesa del Mar, Spain.[4] In July 2002, he won the Qingdao Zhongfand Cup. In the following month, he played on board 4 for the gold medal-winning Chinese team in the Under-16 Chess Olympiad in Kuala Lumpur.[5][6] In July 2004, Wang again won gold with his national team in the U-16 Chess Olympiad in Calicut, India. He scored 8/9 on the first board, a result that also earned him the individual gold medal, producing a rating performance of 2577.[7][8] In the same month he won the "Children of Asia", a youth tournament in Yakutsk, Russia.

Wang's first major tournament win was the Dubai Open in April 2005, when he was still untitled and finished clear first with a score of 7/9 points (rating performance of 2731), ahead of 53 grandmasters and 30 international masters.[9]
In August 2005, Wang won with 10/11 (two points clear ahead of the rest of the field) in the 2nd IGB Dato' Arthur Tan Malaysia Open in Kuala Lumpur (rating performance of 2843).[10]
In October 2005, he came joint-first in the Beijing Zonal 3.3 tournament, and took the second place after a playoff match.[11]

In January 2008, at the 15th Asian Team Chess Championship in Visakhapatnam, Wang won an individual gold medal for his performance on board three (5/6). The national team had also won gold overall.[14]
In March 2008, he won the 23rd Reykjavik Open on tie-break with 7/9 points (2721 rating performance).[15]
In April 2008, Wang competed at the Russian Team Championships in Dagomys, Sochi for the team 64 (Moscow), where he achieved a score of 8.0/11 (+5=6-0) and a performance rating of 2795.[16]
In July 2008, he came 5th out of 10 players at the 9th Karpov International Tournament (Category 18, average Elo rating: 2691) in Poikovskiy, Russia. He scored 5/9 (+2=6-1) with a performance of 2734.[17]
In September 2008, he competed in the 5th Russia v China Match in Ningbo, where he was the top scorer in the men's section with 3½/5 and a performance rating of 2844 playing with Wang Yue, Bu Xiangzhi, Ni Hua, Li Chao for the Chinese men's team.[18]

He has assisted in preparing Levon Aronian for the 2011 Candidate Matches.[22] In a report on the 2010 Tal Memorial, the noted chess journalist Ilya Odessky writes that Levon Aronian "in his teasing style" named Wang Hao as the most talented player of the tournament.[23]

At the 2013 Norway Chess tournament, Wang Hao finished in seventh place with three wins, three draws, and three losses. Wang was tied for last after five rounds, when he lost against the eventual tail-ender Jon Ludvig Hammer. However, he ended the tournament very strongly with two wins over the World Championship finalists Magnus Carlsen and Viswanathan Anand.[26]

In June 2015, Wang Hao scored 6½/9 in the 10th Edmonton International Tournament, tying for the second place with Vassily Ivanchuk and Surya Shekhar Ganguly.[29] On December 31, 2015 Wang won the 4th Al Ain Classic tournament scoring 8/9, 1.5 points ahead of the nearest followers. He already ensured the victory with a round to spare.[30] In March 2016 he won the 6th HDBank Cup in Ho Chi Minh City, Vietnam with 8/9.[31]